This project has the goal of understanding the allosteric modulation, through voltage sensing, of voltage-gated ion channels and GPCRs has on their function. Allosteric modulation of voltage-gated ion channels occurs via domains not directly needed for voltage sensing and gating, that is, the first three transmembrane domains of each monomer, and the linker attaching this domain to the remainder of the protein. Allosteric modulation of GPCR activity occurs through voltage-sensing. Engineered versions of the Shaker potassium channel and the muscarinic acetylcholine receptor type 2 will be expressed in Xenopus oocytes and probed using electrophysiological and fluorescent techniques. The aims are to understand the role the linker between the third and fourth transmembrane domains of voltage-gated potassium channels plays in its function, to understand the movements that occur in the second and third transmembrane domains upon changes in membrane potential, independent of the movement of the primary voltage sensor in the fourth transmembrane domain, and to understand the movements that occur in response to changes in membrane potential in GPCRs. The long-term objectives of this project are to advance our understanding of potential novel targets for therapeutics targeted to modulate the voltage-sensing properties of voltage-gated ion channels and GPCRs. As these membrane proteins are already successful targets for many therapies, improved understanding of how to modulate their function should lead towards improvements of human health.